Sensorineural hearing loss (SNHL), the most common type of deafness affecting more than 30 million Americans, is largely untreatable . When hair cells die, spiral ganglion neurons also may lose their peripheral axons and degenerate. In birds, but not mammals, supporting cells re-enter the cell cycle, divide and differentiate into new hair cells. A promising gene therapy for hair cell regeneration from non-sensory cells that remain in damaged cochlea has been accomplished in mammals for the first time. The gene Atoh 1 (Math-1) induced replacement of hair cells from supporting cells and restored hearing (auditory brainstem responses) in deafened mammals. This project seeks to demonstrate the efficacy of a multi functional nanoparticle (MFNP) targeted delivery system utilizing magnetic forces for delivery of distinct therapeutic payloads, such as Atoh 1 to the mammalian cochlea. Our research team seeks to build upon a solid foundation and pilot data to refine our treatment approaches for SNHL for translation to clinical treatment opportunities. The first segment of the study will characterize the three MFNP carriers and test them for membrane transport and targeting in both cell culture and rodent models. Quantification of the amount of MFNP delivered will be accomplished by using radionuclide tracing, DNA, protein and chromatographic analyses. The second part of the project will demonstrate therapeutic effectiveness in deafened and toxin-injured mouse cochlear cultures. Transfection in the cochlea by a non-viral vector would be a major milestone. The third portion of this study will take the MFNP with it three therapeutic payloads to the next step toward clinical use: delivery to the human cochlea. Temporal bones from cadavers will be used to test delivery of the MFNP. Again, a radionuclide tracing method will be used to quantify how much of the MFNP-payload can be delivered in time by a defined external magnetic field. Successful accomplishment of these aims will validate this technology and prepare for the next step toward clinical development, such as in vivo therapeutic experiments rodents. Magnetic targeting of therapeutic nanoparticles to the ear may lead to a safe, effective and efficient means of treating patients with SNHL and other inner ear disorders by preventing hearing loss and perhaps even restoring lost hearing. PUBLIC HEALTH RELEVANCE: Sensorineural hearing loss (SNHL), the most common type of deafness affecting more than 30 million Americans, is caused by death of hair cells from genetic disorders, age, noise, infection and toxins. SNHL, although amenable to habilitation with devices, is largely untreatable and costs the U.S. public more than $56 B annually. This research project, to develop magnetic targeting of therapeutic nanoparticles to the ear, may lead to a safe, effective and efficient means of treating patients who suffer from SNHL by preventing hearing loss or perhaps even restoring lost hearing.